This invention is concerned with devices for detecting the presence of operating consumer electronic equipment, where such operation by radiating electromagnetic emissions, may interfere with electronic equipment that is mission critical, or used for life support.
Unauthorized use of consumer electronic equipment on airlines, in hospitals and in other areas where potential for interference with flight instrumentation and controls, or life support equipment is an ever increasing problem. For example, in early 1993, a DC-10 on approach to Kennedy Airport in New York, suddenly veered out of its flight pattern. Many believe that the cause of this near tragedy was electromagnetic interference (EMI) from a CD player interfering with the aircraft's navigation system. The use of portable electronic equipment in hospitals has too proved to interfere with infusion pumps and other susceptible medical devices.
The FAA in its regulations (US FAR 91.21) bars the use of any portable electronic device on US registered civil aircraft with certain listed exceptions and exceptions allowed by the operator of the aircraft. Cellular telephones and other active transmitters are banned altogether; however, laptop computers, CD players, calculators and all other electronic equipment are banned only when the plane is in takeoff or landing.
Although the radiated emission limits of consumer electronic equipment (unintentional radiators) must generally fall within the values prescribed in 47 CFR Section 15 Subpart B, particularly 47 CFR .sctn.15.109, usually only a small number of samples of the equipment are tested for certification or verification. Improper manufacture, improper repair, physical damage and the like, can cause a particular piece of consumer electronic equipment to radiate at orders of magnitude above its maximum specified value, and EMI generated by such non-conforming equipment could interfere with the proper operation of aircraft navigation and control systems, or critical life support systems dependent on electronics for their operation.
All avionic equipment on civil aircraft must meet the minimum EMI susceptibility requirements as set forth in specification RTCA/DO-160C (Radio Technical Commission for Aeronautics). FIG. 20-6 of said specification shows that Category T equipment must survive an applied field of 5 v/m from 500 KHz to 400 MHz and rolling off to 0.1 v/m at 10 KHz at 1.0 db/octave. It is possible, that an operating piece of portable equipment (unintentional radiator) taken onto an aircraft will interfere with the more susceptible cockpit instrumentation. Certainly intentional radiators such as CB radios, cellular telephones, pagers, and remote control toys have the ability to interfere with navigation equipment. In contrast, EMI susceptibility design and testing of medical equipment is almost non-existent so that even an FCC conforming class B unintentional radiator may have detrimental consequences on this equipment and the patient dependent upon it.
Prior art related to this invention includes U.S. Pat. No. 4,887,086 titled "Combined Scanner and Radar Detector." Unser et al. use a scanner to detect the presence of transmissions (intentional fixed frequency radiators) on certain FCC allocated radio frequencies and then sound an alarm if any of said frequencies are detected. In U.S. Pat. No. 5,086,300 titled "Method and System for Passive Detection of EM Events," Ashmore discloses a system which is useful for indicating the presence of an electronic fuzing device (unintentional radiator) in aircraft luggage by detecting its electromagnetic emissions.
What is needed is a device which detects the EMI radiated from portable electronic equipment and alerts airline personnel of the presence of such an operating device before it becomes a hazard to the operation of the aircraft without giving off false alarms. Similarly, hospitals need such a device to alert the proper personnel of the presence of devices which may interfere with medical electronics. However in each of these cases the radiation to be detected is not confined to fixed frequencies as in the case of Unser, nor is it fixed to the lower threshold of detection as in the case of Ashmore.